1. Field of the Invention
The present invention relates to a device for controlling the application of glue to the binding of a book or magazine during the book binding process. More specifically the device relates to a computer controlled servo-motor and cam that can precisely adjust the distance from a doctor blade to the glue wheel to precisely control the thickness, and the spatial application, of the glue applied during the book binding process.
2. Description of the Related Art
The process of book binding is well know and the subject of numerous patents. See, for example, U.S. Pat. No. 3,866,568 issued to Minami on Feb. 18, 1975, and U.S. Pat. No. 4,014,287 issued to Green on Mar. 29, 1977 for general information on the book binding process. One of the main steps in bookbinding involves the application of an adhesive to the backbone of the assembled pages of a book or magazine. As used herein, the term bookbinding applies to the binding of any print publication, including books, magazines and catalogues, and the term book is used to refer to the material being bound, whether a book, a magazine, or a catalogue. The adhesive is typically glue, and most commonly the glue is made from petroleum based products. In modern bookbinding it is common to use “hot glue” or glue that is heated and that solidifies when it cools. This form of glue solidifies much quicker than other types of glues. The glue is applied to the book back, often called the spine, of the book by running the spine over a glue wheel or series of glue wheels which are covered with glue that is applied to the spine.
The application of the glue to the backbone is accomplished by means of glue wheels, which typically obtain the glue from a glue pot. The glue pot is a vessel that holds the liquid glue. Generally a portion of the glue wheel sits in the reservoir of glue and as it rolls the outer surface of the glue wheel picks up glue from the pot and transfers the glue to the top of the wheel. The back of the book, which is often referred to as the spine or backbone, is run over the top of the glue wheel to apply the glue. Typically the spine is pressed against the first glue wheel as it rolls across, which forces the pages apart slightly and allows the glue to spread between the pages. It is important to apply the appropriate amount of glue to the book back. If too little glue is applied the pages may not be properly bonded and the book may fall apart, and if too much glue is applied the pages might stick at an inconvenient distance from the spine and prevent the pages from opening. Glue is often the most expensive component of the book binding process, and the use of excess glue leads to waste, which will increase the cost of the binding process. There is the need, therefore, for a system to precisely control the amount of glue on the glue wheel to ensure sufficient glue to properly bind the book, while minimizing the amount of glue used and minimizing waste.
Another commonly encountered problem is that glue may be applied to too much of the spine. In old systems the glue wheel was entirely covered with glue, and the book back would pick up glue from the leading edge to the trailing edge. In general it is not desirable to get glue on the ends of the book back. There are a couple of reasons for this. One reason is that this glue may seep up between the pages and make the pages stick. One other reason is that it is a waste of glue. This is particularly true in binding magazines, where the ends of the bound book are trimmed off. If there is glue on the ends of the book back and pages it will be trimmed off, and will be totally wasted.
A device, known in the art of bookbinding as the doctor blade, is used to control the amount of glue on the wheel and which thus can be imparted onto the spine of the book. An example of a prior art doctor blade can be seen in U.S. Pat. No. 6,565,658 issued to Fischer et al., on May 20, 2003. The earliest doctor blades were fixed and therefore only controlled the thickness of the glue on the glue wheel. Modern doctor blades can move, reciprocating into and away from the glue wheel, from an open position where glue is allowed on the glue wheel, to a closed position, which is close enough to the glue wheel to essentially scrape the glue off the glue wheel and prevent glue from contacting the book back. Prior art doctor blades were typically controlled by a cam drive linkage that was attached to the drive mechanism of the machinery that moved the books through the binder. This system is not precise, and can allow too much or too little glue on the wheel, and also cannot be precisely controlled to prevent glue from adhering to the ends of the spine. There is a need, therefore, for a system to precisely control the thickness of the glue on the glue wheel.